In order to change the tails concentration in a centrifuge cascade of this type, it has been proposed in German Pat. No. 2,746,871 to feed a partial stream of the starting mixture (UF.sub.6) to the first stage of the cascade and to charge the first cascade enrichment stage or the first cascade derichment stage, respectively, with the remaining starting mixture. Charging the first cascade enrichment stage results in a reduction of U.sup.235 concentration in the tails, as compared to the tails concentration when the entire starting mixture is fed into the first stage. Charging the remaining partial stream to the first cascade derichment stage, conversely, results in an increase of U.sup.235 in the tails.
According to this patent, it was possible, in principle, to infinitely vary the tails concentration. However, in addition to high mixture losses, it involved a less than optimum utilization of the individual stages.